A test device for high-temperature testing a target object (hereinafter, referred to as a “wafer”) is provided with a loader chamber 1 and a prober chamber 2 which are arranged to be adjacent to each other as shown in FIG. 3.
The loader chamber 1 shown in FIG. 3 includes a mounting unit 3 for mounting thereon a cassette of wafers W, a wafer transfer mechanism (not shown) for transferring a wafer W from the cassette sheet by sheet and a sub-chuck (not shown) for pre-aligning the wafer W while transferring the wafer W. As shown in FIG. 3, the prober chamber 2 includes a wafer chuck 4 which a wafer W is mounted on and is horizontally moved by an XY table 4A, a card holder 6 provided in the center of a head plate 5 formed above the wafer chuck 4, a probe card 7 held by the card holder 6 and an alignment mechanism 8 for aligning probes 7A of the probe card 7 and electrode pads of the wafer W on the wafer chuck 4. While the wafer chuck 4 is horizontally moved by the XY table 4A, the electrode pads of the wafer W are aligned with the probes 7A by the alignment mechanism 8 and then the wafer W is heated to a predetermined temperature by a temperature controlling mechanism built in the wafer chuck 4 so that a high-temperature test on the wafer W can be performed.
As shown in FIG. 3, the alignment mechanism 8 includes a first imaging unit 8A for photographing the wafer W and a second imaging unit 8B for photographing the probes 7A, and the first imaging unit 8A moves between the rear end of the prober chamber 2 and the probe center through an alignment bridge 8C. The probe card 7 is electrically connected with a test head T via a coupling ring 9.
For example, in high-temperature testing a wafer W, the wafer W on the wafer chuck 4 is heated to around 150° C. by the temperature controlling mechanism provided in the wafer chuck 4 and the electrode pads of the wafer W are aligned with the probes 7A of the probe card 7 by the alignment mechanism 8. After that, the electrode pads of the wafer W are contacted with the probes 7A and the wafer W is overdriven to thereby test the wafer W at 150° C.
At the initial test stage, the wafer W is heated to a high temperature of 150° C. but the probe card 7 is not heated, thereby leading to a considerable temperature difference between the wafer W and the probes 7A. Therefore, if the probes 7A come in contact with the first chip of the wafer W for the test, the probe card 7 is gradually heated by the wafer W provided on the wafer chuck 4 and therefore thermally expands. Due to this thermal expansion, the position of the needle tip of the each probe 7A changes from the position where the needle tip has been aligned, which results in contact defects between the probes 7A and the electrode pads.
Disclosed in Japanese Patent Laid-open Publication No. 2004-266206 is a technique for preventing thermal expansion of a probe card 7, i.e. a main body, and probes 7A in the test by heating the probe card 7 to a test temperature with a heating plate used only for pre-heating just before the test. Further, while a wafer W mounted on a wafer chuck 4 is exchanged with a next wafer W, in order to prevent contraction of the probe card 7 due to cooling caused by separating the wafer chuck 4 from the probe card 7, the probe card 7 is maintained at the test temperature by the heating plate used only for pre-heating. However, in this technology, part of the probe card 7 protruding from the wafer chuck 4 during a test is cooled as shown in FIGS. 4A and 4B. If probes 7A1 in a cooled part of the probe card 7 come in contact with the wafer W by index-feeding of the wafer W, they may not make a sufficiently good contact with the electrode pads of the wafer W because the probes 7A1 are cooled and contracted more than the contacted probes 7A and therefore their tips become more distant from the wafer surface than those of the probes 7A do, which makes it difficult to test the devices of the wafer contacted with that part at a high temperature.
FIG. 4A shows a wafer W divided into four parts which are tested in an order of (1) to (4) and the dot part 7A1 indicates the probes protruding from the wafer chuck. Further, FIG. 4B is a side view of the probe card 7 in contact with the wafer W taken along the line B-B of FIG. 4A.